Curable organopolysiloxane compositions curable by a hydrosilylation reaction are used as protective or coating agents in the manufacture of semiconductor parts of optical semiconductor devices, such as photo-couplers, light-emitting diodes, solid state imaging elements, etc. Since the light received by the optical elements or emitted from these elements passes through the layers of the aforementioned protective or coating agents, it is required that they should neither absorb nor dissipate the light.
The curable organopolysiloxane composition that after curing by a hydrosilylation reaction forms a cured product having high transmittance and index of refraction can be exemplified, e.g., by a curable organopolysiloxane composition comprising: an organopolysiloxane that contains in one molecule at least two alkenyl groups and at least 20 mole % of all silicon-bonded organic groups in the form of aryl groups; an organopolysiloxane that contains silicon-bonded hydrogen atoms; an organopolysiloxane that contains in one molecule at least 5 mole % of all silicon-bonded organic groups in the form of alkenyl groups, at least 5 mole % of all silicon-bonded organic groups in the form of aryl groups, at least 5 mole % of all silicon-bonded organic groups in the form of alkoxy groups, and at least 5 mole % of all silicon-bonded organic groups in the form of epoxy organic groups; and a hydrosilylation catalyst (see Japanese Unexamined Patent Application Publication (hereinafter referred to as “Kokai”) 2007-327019). Another example is a curable organopolysiloxane composition comprising: an organopolysiloxane that contains in one molecule at least 0.5 mole % of all silicon-bonded organic groups in the form of alkenyl groups and at least 25 mole % of all silicon-bonded organic groups in the form of aryl groups; an organopolysiloxane that contains in one molecule on average at least two silicon-bonded aryl groups and on average at least two silicon-bonded hydrogen atoms, and a hydrosilylation catalyst (see Kokai 2008-1828).
However, the above-mentioned curable organopolysiloxane compositions produce cured products which have low optical transmittance and in addition to this can be easily peeled from substrates since they have poor adherence to the substrate surfaces.
It is an object of the present invention to provide a curable organopolysiloxane composition that produces a cured body having a high index of refraction, high optical transmittance and good adherence to substrates. The invention also provides a semiconductor device that has semiconductor parts of excellent reliability due to coating thereof with a cured body of the aforementioned composition.